Desaturating an image is simple. Just press CTRL+SHIFT+U. You can also colorize it with Hue/Saturation. But your choice is limited. What do you do when you want to change a color image to a single color of your choice? It's very simple and can be done in any version of Photoshop.
Here is a free stock image.
The same image with a single tone.
The Photoshop tutorial is here
Other photoshop tutorials are here
